Gas piston operated automatic gun



Nov. 21, 1961 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN '7Sheets-Sheet 1 Filed Sept. 24, 1947 in V6 27 for PauZ ff. Dix-0n Nov.21, 1961.

Filed Sept. 24, 1947 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN 7Sheets-Sheet 2 Inventor Paul /7213211071 '7 Sheets-Sheet 3 P. H. DIXONGAS PISTON OPERATED AUTOMATIC GUN Nov. 21, 1961 Filed Sept. 24. 1947 xvwg @N v w was In were Paul HDz'xorz Nov. 21, 1961 P. H. DIXON GAS PISTONOPERATED AUTOMATIC GUN 7 Sheets-Sheet 4 Filed Sept. 24, 1947 'III 1YIIIIIIIII in we n Mr Paul H. Dixon '7 Sheets-Sheet 5 In ventor" Paul H.Dix-0n Nov. 21, 1961 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN FiledSept. 24, 1947 Nov. 21, 1961 P. H. DIXON PISTON OPERATED AUTOMATIC GUNGAS 7 Sheets-Sheet 6 Filed Sept. 24, 1947 Inventor FauZHDz'won Nov. 21,1961 P. H. DIXON 3,009,396

GAS PISTON OPERATED AUTOMATIC GUN Filed Sept. 24, 1947 '7 Sheets-Sheet'7 in venzm Paul fiDz'x'on B hi 0 United States Patent 3,009,396 GASPISTON OPERATED AUTOMATIC GUN Paul H. Dixon, Rockford, 111., assignor toUnited Shoe Machinery Corporation, Flemington, N.J., a corporation ofNew Jersey I Filed Sept. 24, 1947, Ser. No. 775,844 1 Claim. (Cl.89-191) This invention relates to ordnance and is herein illustrated asembodied in an automatic 20 mm. gun or. cannon which will operateeffectively at a very high cyclic rate and is especially useful inairplanes.

The present invention consists in the novel features hereinafterdescribed, reference being had to the accompanying drawings illustratingone embodiment of the invention which is fully disclosed in thefollowing description and claim.

In the accompanying drawings,

FIG. 1 is a plan view of the rear portion of the illustrative gun;

FIG. 2 is a vertical section on line II-II of FIG. 1; a bolt assembly ofthe gun being shown in its battery position ready for the firing of thegun;

FIG. 3 is a vertical section on a forward extension of line II-II ofFIG. 1 showing a recuperator of the gun;

FIG. 4 is a horizontal section on line IVIV of FIG. 2;

FIG. 5 is a view similar to FIG. 2 showing the gun after it has beenfired and the bolt assembly has been moved to its fully recoiledposition;

FIG. 6 is a section on line VI--VI of FIG. 4 illustrating cartridgefeeding and electric ignition mechanism of the gun;

FIG. 7 is a section on line VII-VII of FIG. 4 showing a reaction unit ofthe gun;

FIG. 8 is a section on line VIII--VIII of FIG. 2;

FIG. 9 is a perspective view partly in section on line IXIX of FIG. 2showing the forward end of a bolt and a feed box of the gun;

FIG. 10 is a section on line X-X of FIG. 2;

FIG. 11 is an enlarged vertical central section of portions of the boltand a slider of the bolt assembly;

FIG. 12 shows in perspective -a gas operated piston forming part of anammunition feeder of the gun;

FIG. 13 is a section on line XIIIX[II of FIG. 10;

FIG. 14 shows in perspective the bolt assembly and a bolt lock which maybe secured to and forms in effect part of the receiver of the gun;

FIG. 15 is an exploded view of the bolt assembly illustrated in FIG. 14;

FIG. 16 shows in perspective the bolt and portions of the slider and awedge forming part of the bolt assembly; the bolt being in a lockedbattery position in front of portions of the lock;

FIG. 17 is a perspective view illustrating portions of bolt assemblyguides or rails of the receiver and cartridge case deflecting camsformed on said rails;

FIG. 18 is an exploded view showing portions of a cradle and arecuperator, which cooperate to support the gun for sliding movement inrecoil and counter-recoil, and also showing a bracket for locking thegun in operative position in the cradle and the recuperator; and

FIG. 19 is a section on line XIXXIX of FIG. 3.

The illustrative gun is mounted in a cradle 40 which may be secured to aturret (not shown) of an airplane for example, said gun being movable inrecoil and counter- 3,009,396 Patented Nov. 21, 1961 through mechanismhereinafter described, to the cradle, and a recoil spring nut '48 (FIG.3) which is threaded onto a barrel 50 of the gun and may be consideredas part of the barrel.

The barrel 50 is threaded into a receiver 52 and is properly positionedlengthwise in and secured to the receiver by a screw 54 (FIGS. 2, 4 and5) which is threaded into the receiver and fits in a recess 56 in thebarrel. The gun is provided with a breechblock or a bolt 58 having arear T-shaped tongue or projection 60 (FIGS. 4, 14, 15 and 16) fittingin a complemental vertical or transversely extending guideway 62 at theforward end of a slider 64, said bolt and, slider which, together with awedge 66, may be referred to as a bolt assembly, being guided formovement in recoil and counter-recoil by longitudinally extending railsor guides 68 (FIGS. 2, 4, 5, 6, 7 and 17), faces 70 (FIGS. 4, 6 and 7),72 (FIGS. 2,5,6 and 7) of the receiver 52 and faces 70a, 72a (FIGS. 8, 9and 14) of bolt locks 82. As will be explained later, the rails '68 areformed in part by forward extensions 74 of a drum 76 of a reaction unit78 and by abutments or rail portions 80 (FIGS. 4, l4 and 16) of the boltlocks 82 which fit in complementally shaped recesses 84 (FIGS. 4, 5, 8and 9) of the receiver 52 and each of which is secured to said receiverby a nut and screw 86 (FIGS. 4, 5 and 6) and may be considered as partof the receiver. The major portion of an inside face 88 of the cradle 40is cylindrical and forms a guideway with which cylindrical outside faces90 (-FIGS 1, 2, 4, 5 and 7) of the receiver slidingly engage, upwardlyand downwardly disposed projections 92 (FIGS. 1, 2, 5 and 10), 94 (FIGS.2, 5, 6, 7, 8 and 10) of the receiver engaging in guideways 96 (FIGS. 1and 10), 98 (FIG. 10) formed by spaced pairs of flanges 100, 102 formedin the cradle.

The slider 64 has a depending lug 104 (FIGS. 2, 5, 6, 7, 14 and 15)provided with a recess 106 for receiving the rear end of a spring 108fitting into a recess 110 of a shank 112 of the wedge 66. The wedge 66has a T- shaped guideway 114 (FIGS. 2, 5, 9 and 15) extendinglongitudinally and transversely of the receiver for receiving a T-shapedprojection 116 (FIGS. 9 and 15) at the lower end of the bolt 58, thedepending lug 104 of the slider being provided with a pair of guideways118 (FIGS. 6, 7, l4 and 15) for receiving bifurcations of the shank 112of the wedge 66. The wedge 66 is moved rearward, by mechanismhereinafter described, upon the slider 64 until faces 120 (FIGS. 9, 14,15 and 16) of the bolt 58 engage faces 72a (FIGS. 8, 9 and 14) of thebolt lock 82, at which time channels 124 of the bolt are in registerwith rail engaging channels 126 respectively of the slider 64, the bolt,which is then in its lowered or forward unlocked position, thereafterbeing moved, together with the slider and the wedge 66 in recoil alongthe rails 68, which may be described as including the abutments 80(FIGS. 4, l4 and 16) of the bolt lock 82, rearward or in recoil withoutsubstantial resistance and thereafter against the action of the reactionunit 78 to their fully recoiled position shown in FIG. 5.

As above explained, the rails 68 are formed in part by the rail portions74 (FIGS. 2, 4, 5 and 7) of the drum 76 which forms part of the reactionunit 78, said rail recoil in the cradle approximately one-quarter of an.

housing assembly 46 (FIGS. 3, 18 and 19) secured,

portions fitting in slots 128 of the receiver 52 in alinement with theportions of the rails formed integral with the receiver. The lateralbearing faces 70 of the receiver 52 extend from the bolt lock 82 to thereaction unit 78 and are engaged by the opposite faces 130 (FIGS. 4, 14,15 and 16), 132 of the slider and the bolt to assist in guidingthese'members in recoil and counter-recoil in the receiver 52. Thereaction unit housing portion 134 (FIGS. 2, 4, 5 and 7) of the receiver52 is cylindrical and accordingly the portions 74 of the rails 68extending into said reaction unit housing portion engage the bottoms ofthe channels 126, 124 of the slider 64 and the bolt' 58 effectively toguide these members without the assistance of the lateral bearing faces70 of the receiver;

The bolt 58 is moved to, and is held in, its raised battery positionshown in FIG. 2 by the wedge 66, the construction and arrangement beingsuch that when the bolt is in it's lowered unlocked position inengagement with the rear end of the barrel 50 after chambering acartridge 136 (FIGS. 1, 2 and 5), the wedge 66 under its own momentumand assisted by the spring 108, is moved forward causing the bolt to beraised to its battery position, rear faces 138 (FIGS. 14, 15' and 16) ofthe bolt then being in front of and in engagement with front faces ofthe abutrnents 80 and flanges 142 of the bolt lock- 82 to lock the bolt58 and accordingly the bolt assembly against recoil movement. The slider64 may be said to be slidingly coupled to or interlocked with the bolt60* and the wedge 66.

After the gun has been fired the bolt 58 is lowered from its raisedbattery position, to unlock it, by rearward movement of the wedge 66acted upon by a piston 144 (FIGS. 2, 5, 8, 9 and which is slida'ble in acylindrical recess 146 formed in the downwardly projecting portion 94 ofthe receiver 52 and acts against the front face of the wedge 66. It willbe noted that the bottom of the bolt 58 has formed in it a tunnel 148(FIGS. 2, 5 and 9) to permit rearward movement of the piston 144 withoutinterfering with the free lowering of the bolt. The piston 144 has ashank portion of reduced diameter, an expansion chamber 150 (FIGS. 2, 5and 10) being formed between the cylindrical recess 146 and the shankportion of the piston. Between the chamber 150 and a bore 152 of thebarrel 50 is a gas passage 154 (FIGS. 2 and 5) formed in part by arestricted orifice in a silver heat dissipating plug 156 housed in arecess 158 of the barrel.

When the gun is fired the receiver 52, together with l the various gunparts supported by it, moves approximate ly one-quarter of an'inch inrecoil along the inside faces 88- of the cradle 40 against the action ofthe recuperator 44 (FIGS. 3 and S) and then moves back to batteryposition under the action of said recuperator. In the meantime, highpressure expanding gases from the. bore 152 of the barrel 50 passthrough the passage 154 into the chamber 150 forcing the piston rod 144with considerable pressure against the front face of the wedge 66. Whenthe gun is first fired the rearward force of the explosion against acase160 of the expended cartridge 136 forces the bolt 58 against front facesof the abutments 80' and the flanges 142 of the bolt lock 82 with somuch force that the piston 144 acting through the wedge 66 does not havesufiicient power to move the bolt to its lowered unlocked position. Whenthe receiver 52 is near the end of its recoil movement the pressure inthe bore 152 of the barrel 50 will have been reduced sufficiently toinsure against gases entering the receiver and rearward pressure of thepiston 144 acted upon by the expanding gases in the chamber 150 movesthe wedge 66 rearward against the action of the spring 108 to a rearwardposition upon the slider 64 and thus draws the bolt 58 downward untilthe faces 120 (FIGS. 9, 14, and 16) of the bolt'58 engage the faces 72aof the bolt lock 82of the receiver 64, at-which time the grooves orchannels 124 of the bolt are in register with the abutments 80 of thebolt lock 82. The bolt 58, the slider 64 and the wedge 66 guided by therails 68 and the lateral bearing faces 70 of the receiver 52 are thenmoved in recoil under the action of the gas actuated piston 144 with theassistance of the blow-back action of the case of the expended cartridge136 against the bolt. As explained in application for United StatesLetters Patent Serial No. 716,469, filed December '16, 1946 in my name,it is sometimes desirable to insure against any unburned gases enteringthe receiver '52,- in which event the gas passage 154 is restrictedsufficiently to delay wedge actuating movement of the piston until a 4substantially all the unburned gases have left the bore 152 of thebarrel 50.

The reaction unit 78 comprises a recessed plate '162 (FIGS. 2, 4, 5 and7) which fits slidingly in the housing portion 134 of the receiver 52and is normally forced against a transverse shoulder 164 of the receiverby a spring 166. The spring 166 is initially compressed by theretaining. drum 76 held in the housing portion 134 of the receiver 52 bya threaded rear cover 168 (FIGS. 2, 4 and 5) which is screwed into therear end of the receiver and is locked in'its operative position in saidreceiver by a spring-pressed plunger 170 (FIGS. 2 and 5) slidinglymounted in the cover and constructed and arranged to enter a hole 172 ofthe receiver. As the bolt assembly is moved in recoil, opposite faces174 (FIGS. 14, 15 and 16) of the slider 64 and opposite faces 176 of thewedge 66 engage the plate 162, the spring 166 being compressed to absorbthe energy of the bolt assembly and .to effect movement of said assemblyin counter-recoil.

Cartridges 136 assembled in a belt 177 (FIGS. 1 and 6) are automaticallyfed successively into a centralized ram ming position shown in FIG. 5(dash line position FIG. 6) in the receiver 52 of the gun, by anammunition feeder 178 (FIGS. 1, 6 and 9) such as is fully disclosed inan application for United States Letters Patent Serial No. 764,790,filed July 30, 1947 in my name. Cartridges 136 in the belt 177 are feddown through a chute 180 to a carrier or sprocket 182 rotatably mountedin a feed box 184 which has at its forward end a pair of lugs 186 (FIGS.7 and 9) constructed and arranged to fit in channels 188 of the cradle40 and which has rearwardly extending arms 190 (FIGS. 1, 2, 5 and 7)spaced to include between them an upstanding boss 1-92 of the cradle,said arms being.

to accommodate clips 202 (FIGS. 1 and 6) of the cartridgebelt 177 andwhich have outwardly curved-forward ends 204 (FIGS, 1, 2 and 5)constructed and arranged to cooperate with a rammer 206 hereinafterdescribed and. formed integral with the bolt 58 for chambering thecartridge. The sprocket 182 is tion at the cyclic rate of the gun by aworm 208 (FIGS. 1, 2, 5, 8' and 9) mounted upon a piston210 which isreciprocable but not rotatable in a cylinder 212 (FIGS. 2, 5, 10 and 13)formed in part by a sleeve214 secured to the receiver 52, and which isoperated by expanding gases admitted to an intermediate bore 216 (FIGS.2, 5 and '13) of the sleeve through a passage 21 8 extending through thebarrel 50, the receiverv 52 and the sleeve'212. The p'assag'e'218 isformed in part by a restricted bore or passage 220 through a silver plug222 housed in a pocket of the barrel.

In' splined .relation with the sprocket 182 and held against'a shoulderof said sprocket by a pair of spring- .pressed locking arms 219 (FIGS.1, 2, 5 and 9) is a nut 223 (FIGS. 2, 5 and 8) having internal spiralthreads meshing withex'ternal spiral threads of the. worm 208 which, aswill be hereinafter explained, during rearward 'movement'of the piston 210 under the action of expanding gas pressure in the sleeve 214, issecured against rotation on the piston.

The piston 210 is secured against rotation in the sleeve 214 by aplurality of longitudinal channels 224 (FIGS. 5 and 13) forming part ofthe sleeve and shaped and arrangedto receive slidingly longitudinalflanges 226 (FIGS. 2, 5, 12 and 13) formed in the piston. The gun partsare in 'their positions shown in "FIG. 2 when the initial round of aburstof cartridges 136 is fired, expanding gases -in the bore 152 of thebarrel 50 thereafter traveling through the passages 218, 220 into theintermediate bore 216 ofthe sleeve .214 and around a flange 228 of thepiston 210 into a-large bore 230 (FIGS. 2, 3,5, 10 and 13) of thesleeve. The forward end of the sleeve 214 is closed rotated step by stepin timed relaby a plug 232 (FIGS. 1, 2, 3, and which is forced into saidsleeve by a collar 234 carried by the barrel 50 and backed up by aflange on said barrel, the plug being inserted in the bore 230 of thesleeve 214 at the time that the barrel is threaded into the receiver 52.When the piston 210 is in the position illustrated in FIGS. 2 and 13high pressure gases admitted to the intermediate and large bores 2116,230 of the sleeve 214, which bores at that time are in'communication,cause rearward movement of the piston by reason of unbalanced gaspressure against opposed faces 236, 238 of the flange 228 of the pistonand a face 239 (FIGS. 2, 5, 12 and 13) at the forward end of thelongitudinally flanged portion 226 of said piston with the result thatfour recesses 240 (FIGS. 2 and 5) (only one shown) in the piston moveinto interlocking relation with opposed studs 242 at the forward end ofthe worm 208, then in its forward position shown in FIG. 2. The piston210 thereafter causes the worm 208 to slide rearward with it until therear end of said worm engages a transverse face 244 (FIGS. 2 and 5) ofan axially extending bore 246 in the sprocket 182, movement of thepiston being resisted by a spring 248 housed in the bore and having itsforward end in engagement with a collar 250 secured to the piston.

Rearward movement'of the Worm 208 in meshing engagement with the nut 223and interlocked against rotation upon the piston 210 will effectclockwise rotation of the sprocket 182, as viewed in FIG. 6, causing theleading cartridge 136 in the belt 177 to be forced against the slider 64and the bolt 58, which at that time are moving in recoil and are in suchpositions as to prevent the cartridge from being moved to its central orramming position shown in FIG. 5 (dash line position as shown in FIG. 6)in the receiver 52. After the bolt.58 has moved to a recoil positionrearward of and out of engagement with the leading cartridge 136 in thebelt 177, the piston 210 is moved further rearward by the expandinggases until the worm 208 engages the face 244 of the bore 246 in thesprocket 182 at which time said leading cartridge in the belt is in itscentral or ramming position and the sprocket may be said to be in itsindexed position. The sprocket 182 is held in its indexed position by aspring-pressed plunger 249 (FIGS. 1 and 8) which is slidingly mounted ina guideway 251 of the feed box 184 and has its lower end in engagementwith one of four recesses 253 (FIG. 8) in the nut 223.

When the bolt 58 is in battery position the rear end of the cartridge136, as illustrated in FIG. 2, is in engagement with a vertical face 254(FIGS. 2, 4, 5 and 9) of a recess 256 (FIG. 9) in the forward end of thebolt which has ramming faces 258 and slots 260. After the gun has beenfired and the bolt 58 has been moved to its lowered unlocked positionready to be moved in recoil together with the slider 64, the upper edgeof the rim 262 of the case 160 of the spent cartridge 136 is in theslots 260 with the result that said case, upon recoil movement of thebolt, is extracted from a cartridge chamber 264 of the bore 152 of thebarrel 50. As the case 160 of the spent cartridge 136 is extracted fromthe cartridge chamber 264, the upper edge of its rear end engages camsurfaces 266 (FIGS. 5 and 17) of the rails 68 causing said case to bedeflected downward through alined openings 268, 270 (FIGS. 2, 5, 6 and9) formed in the receiver 52 and the cradle 40 respectively. The bolt 58may be said to comprise the rammer or spaced arms 206 which extend orproject forwardly from the upper lateral portions of the vertical face254 and have undercut opposing faces, the slots 260 being formed in saidarms and having their rear faces continuous with said vertical face.

As the bolt assembly is moved forward in counterrecoil the faces 258 ofthe rammer 206 engage the rear end of the cartridge 136 then in the belt177 and in ramming position, causing the forward end of said cartridgeto be moved forward and deflected downward out of its associatedcartridge clip 202 of the belt by reason of the cooperative action ofthe forward portion 204 of the pocket 196 of the sprocket 182 and thecartridge clasping clip 202 of the belt. As soon as the cartridge 136leaves the belt 177 its rear and drops below the faces 258 of the rammer206 and is engaged by the vertical face 254 of the bolt 58, continuedforward movement of the bolt causing the cartridge to be chambered, therim 262 during the chambering action being raised into the slots 260 inthe bolt. As soon as the bolt 58 engages the rear end of the barrel 50the wedge 66 under its own momentum and actuated by the spring 248 movesforward to its battery position shown in FIGS. 2 and 16 causing the bolt58 to be raised to its locked battery position in which the rear faces138 of the bolt are locked in front of the flanges 142 and the abutmentsof the bolt lock 82.

The cartridge 136 is fired electrically by an electrode or firing pin272 (FIGS. 2, 4, 5, 9, 11 and 15) which is mounted for sliding movementin an insulating sleeve 274 secured to the bolt 58 and has fixed to it acollar 276 (FIGS. 11 and 15) the electrode being constantly urgedrearward with relation to the bolt by a spring disk washer 278, theforward end of the electrode at the time the bolt is unlocked beingpositioned just behind the face 254 of the bolt. Secured to the collar276 of the electrode 272 is an insulating disk 280 which by the actionof the spring disk washer 278 is forced against and slides along a face282 (FIG. 11) of the slider, which face constitutes a stop, as the bolt58 is raised to and lowered from its locked battery position.

When the bolt 58 is in its locked battery position shown in FIGS. 2 and11 the rear end of the electrode 272 is in engagement with an inclinedforward surface 284 (FIG. 11) of a rod or conductor 286 (FIGS. 2, 4, 6,11 and 16) positioned in a longitudinal recess 288 (FIGS. 4, 5 and 11)of the slider 64 and mounted for longitudinal sliding movement ininsulating blocks 290, 292 (FIG. 11) secured to the slider. The rod 286is constantly urged to the right as viewed in FIG. 11 to a position inwhich a flange 294 of the rod is substantially in engagement with theinsulating block 290, by a spring 296 (FIGS. 2, 11 and 16) whichencircles the rod and the forward and rear ends of which the flange 294and a spacer block 298 (FIGS. 2, 5 and 11) carried by the rod. Securedto the rod 286 and arranged between the spacer block 298 and theinsulating block 292 is a conductor 300. The rod 286, together with theparts mounted on it, is inserted in its proper position in the slider,the insulating block 292 being pressed forward into position in theslider and held in such position by a snap spring 302 (FIGS. 7, ll, 14and 15). During the forward end of the counter-recoil movement of theslider 64 the conductor 300 engages a flexible leaf spring 304 (FIGS. 4and 6) which is mounted in an insulating tube 306 secured to thereceiver 52 and is in sliding engagement with a leaf spring conductor308 secured to a screw 310 fixed to the cradle 40, current beingsupplied to the screw by a cable 312 leading to a source of power. Asthe slider 64 moves forward in counter-recoil the conductor 300 engagesthe energized leaf spring 304 and as the bolt 58 is raised to itsbattery position the rear end of the electrode 272 carried by the boltengages the front face 284 of the spring-pressed rod 286 which moves thecollar 276 of the electrode 272 to the right (FIG. 11) against theaction of the spring washer 278 thereby causing the forward end of saidelectrode to project slightly beyond the face 254 of the bolt 58 inorder to contact the rear end of the chambered cartridge 136 to firesaid cartridge.

Guns of airplanes are commonly overhauled after each mission, andaccordingly, it is desirable that burned out guns be quickly removedfrom their cradles 40 and overhauled guns be substituted therefor. Withthe foregoing consideration in view, a cylindrical spring housing 314(FIGS. 2, 3, 5, l8 and 19) forming part of the recuperator 44 has formedintegral with it a pair of laterally extending flanges 316 (FIGS. 18and, 19) ,which are con-r struct'ed and arranged to fit in arcuate slots318 formed in the cradle 40. Before removing the burned out gun from thecradle the feed' box 184 is removed. from-the cradle by removing the pin194 and lifting said box from the cradle. After removing a lockingbracket 320 (FIGS. 3, 18 and 19), which will be described later, fromits locking position on the gun the spring housing 3.1.4 is rotateed 90until its flanges 316 are in dash-line position shown in FIG.. 18, thereceiver then being slid forward outthrough the front of'the cradle 40.

In mounting a reconditioned gun in the cradle, the receiver of the gunis slid rearward into the cradle and the spring housing 314 is thenrotated causing its flanges 316 to. engage in the arcuate grooves 318 ofthe cradle, said housing thus being secured against lengthwise movementin the cradle. To insure against displacement of the spring housing 314thus positioned in the cradle 40 there is provided the above-mentionedlocking bracket 320 (FIGS. 3, 18 and 19) which has a circular portion322 constructed and arranged to fit slidingly on the spring housing 314and which, when arranged in itslocking position, has upper and lowerplates 324, 326vthereof in enaggement with upper and lower surfaces 328,330' respectively of the cradle, inturned ends of arms 332 extendingforward from the circular portion 322 fitting in slots 334 of the springhousing, and four rearwardly extending lugs 336 fitting in grooves 338respectively of the cradle 40, the construction and arrangement beingsuch that the spring housing is held against rotation on the cradle. Itwill thus be apparent that the guns may be quickly and effectivelyremoved from and assembled in the cradle. 7

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

An automatic gun comprising a barrel, a receiver which is secured to thebarrel and has longitudinal guides, a bolt lock having abutments whichare in alinement with said guides, a slider movable longitudinally ofthe 8. receiver in recoil and counter-recoil upon said guides and saidabutments, a bolt which is coupled for longitudinal movement with theslider and is slidableheightwiseof the receiver with relation to theslider, said bolt having;

at its lower end a projection extending longitudinally and heightwise ofthe receiver, a wedg'eymounted for longitudinal movement upon the sliderand having a guideway which extends longitudinally and heightwise of thereceiver and is constructed and arranged slidingly to receive theprojection of the bolt, a stop carried. by the receiver, and a gasoperated piston movable a short distance in recoil under the action'ofhigh pressure expanding gases. between a battery position adjacent tothe Wedge and a rest position against the stop, said piston duringmovement from its battery to its rest position being adapted to move thewedge rearward upon the slider thereby eifecting heightwise movement ofthe bolt upon the slider from a raised locked position in front of theabutments of the bolt lock to a lowered unlocked'position and then toimpart to the wedge sufficient energy to move the wedge together withthe slider and the bolt as a unit a substantial distance in recoil.

References Cited in thefile of this patent UNITED STATES PATENTS.

Nedihardt Mar...

